In UMTS (Universal Mobile Telecommunications System) networks, for the purpose of improving spectral efficiency and further improving data rates, by adopting HSDPA (High Speed Downlink Packet Access) and HSUPA (High Speed Uplink Packet Access), it is performed exploiting maximum features of the system based on W-CDMA (Wideband Code Division Multiple Access). For the UMTS network, for the purpose of further increasing high-speed data rates, providing low delay and the like, Long Term Evolution (LTE) has been studied (Non-patent Document 1).
In the 3G system, a fixed band of 5 MHz is substantially used, and it is possible to achieve transmission rates of approximately maximum 2 Mbps in downlink. Meanwhile, in the LTE system, using variable bands ranging from 1.4 MHz to 20 MHz, it is possible to achieve transmission rates of maximum 300 Mbps in downlink and about 75 Mbps in uplink. Further, in the UMTS network, for the purpose of further increasing the wide-band and high speed, successor systems to LTE have been studied (for example, LTE Advanced (LTE-A)). Accordingly, it is expected that such a plurality of mobile communication systems coexists in the future, and it is conceivable that configurations (base station apparatus, mobile terminal apparatus and the like) capable of supporting the plurality of systems are needed.
In downlink of systems (LTE systems) of LTE, CRS (Common Reference Signal) that is a reference signal common to the cell is defined. The CRS is used in demodulation of transmission data, and is also used in measurement of channel quality (CQI: Channel Quality Indicator) of downlink for scheduling and adaptive control, and measurement (mobility measurement) of downlink propagation path states in an average manner for cell search and handover.
Meanwhile, in downlink of systems (LTE-A systems) of LTE Advanced is defined CSI-RS (Channel State Information-Reference Signal) dedicated to CQI measurement, in addition to the CRS.